A Facile Method for Preparation of Novel Cyclopropanespirohydantoins

A facile synthetic approach to 3'-substituted-5-cyclopropanespirohydantoins has been developed and used to synthesize some new spirohydantoins. The key aspect is the preparation of α-carboethoxy isocyanate basing on Curtius rearrangement, which can be ring-closed to the expected spirohydantoins after the reaction with various amines and hydrazines. Interestingly the cyclopropane ring doesn't open during the whole process.